Give the poor buggers a sand substrate, they're Eartheaters.
Cliffs from Thomas Weidners "South American Eartheaters"
- Extremely low pH, 4.5
- Barely measureable hardness (so 2-3 dgH I'd imagine)
- Substrate spawners, in sand pits (not gravel - 0.2-0.8mm grain size)
- Post-spawn they then cover eggs with sand, up to 5cm (2")
- Removed sand 72 hours later to find small larvae
- The larvae are then spat and re-covered with 5cm of sand
- After a total of six days they were freeswimming and feeding from the sand and were then introduced to Artemia etc. by the keeper.
Should cover it. In conclusion, get sand.